With the growing popularity in recent years of large-size screen and wall-mounted televisions as the interactive information terminals, there are available many kinds of display devices for this purpose such as liquid crystal display panels, field emission displays, electro-luminescence displays, and the like. Among these display devices, plasma display panels (hereinafter referred to as “PDP”) draw attention as being thin display devices for such reasons that they are the self-illuminant type capable of displaying exquisite images and easy to enlarge the screen size, and the development efforts are thus being made toward higher definition and larger screen sizes.
A PDP comprises a front plate having such structure elements as a display electrode, a dielectric layer and a protective layer formed thereon, and a back plate having such structure elements as an address electrode, barrier ribs and phosphor layers formed thereon, wherein the front plate and the back plate are arranged in a manner that they confront each other to internally form minute discharge cells, and their peripheries are sealed with a sealing material. The discharge cells are filled with a discharge gas comprised of a mixture of neon (Ne), xenon (Xe), and the like gases at a pressure of about 66,500 Pa (approx. 500 Torr).
On the front plate, the dielectric layer is formed to cover the display electrode and the protective layer is formed further to cover the dielectric layer, and that a metallic electrode of thick film is used partly for the display electrode to ensure a good electrical conductivity. This causes the protective layer to rise in an area around the display electrode, and makes the risen portion of the protective layer to come in contact locally with the barrier ribs when the front plate and the back plate are placed to confront each other. In such a condition, there has been a case that parts of the barrier ribs where the protective layer is in contact become damaged when the PDP receives vibration or impacts. Since the barrier ribs in the areas corresponding to the display electrode of the front plate are in the vicinity of discharge regions of the individual discharge cells, the phosphor layers are scattered by the damaged barrier ribs, which adversely affects discharging conditions in the discharge cells, thereby giving rise to such problems as an increase in discharge voltage, errant discharges to the adjoining discharge cells and point defects such as lighting errors.
Some techniques are known such as an example, in which the barrier ribs are composed of a double-layered structure, and a black porous layer having a principal ingredient of aluminum oxide (Al2O3) is formed on the barrier ribs as a cushioning material in order to prevent damages to the barrier ribs (refer to patent document 1, for example).
On the other hand, some other techniques relating to height of the barrier ribs are also known for the purpose of improving brightness of a PDP having barrier ribs of a lattice like configuration formed of vertical barrier ribs and horizontal barrier ribs, such as an example, in which heights of the barrier ribs are partially changed by providing salient portions on the vertical barrier ribs to improve an exhaust efficiency in the discharge spaces, and another example, in which ridges of the barrier ribs orthogonal to the address electrode are formed into a concaved configuration to ease exhausting and charging of gases (for example, refer to patent documents 2 and 3).
A demand exists, however, for further miniaturization of the discharge cells in response to the need of advancing high resolution of the display images in recent years. In order to achieve such fine discharge cells with high quality and high yield, and to realize display images of high quality, there still exists a demand to develop a novel discharge cell structure that is not liable to damages to the barrier ribs due to dropping or vibration in spite of their smaller wall thickness, and capable of reducing an effect of irregular discharges between the adjacent discharge cells, or discharge cross-talks.
On the other hand, although the patent document 1 discloses a barrier rib structure that improves robustness of the barrier ribs, it is considered not sufficient to avoid damages to the barrier ribs of thin walls such as those of minute discharge cells required for full high-definition televisions, and it is also not effective to prevent the discharge cross-talks between the adjacent discharge cells. Furthermore, even though the patent documents 2 and 3 disclose the examples relating particularly to height of the barrier ribs in view of improving efficiency of exhausting and charging the gases, as they pertain to the barrier rib structure of lattice like configuration effectual for improving brightness of the minute discharge cells, they are deemed not effective as means to prevent damages to the barrier ribs and suppressing the discharge cross-talks.
Patent Document 1: Japanese Patent Unexamined Publication, No. 2004-158345
Patent Document 2: Japanese Patent Unexamined Publication, No. 2001-093425
Patent Document 3: Japanese Patent Unexamined Publication, No. 2001-126624